1. Field of the Invention
The present invention relates to a negative-type photosensitive resin composition. More specifically, it relates to a negative-type photosensitive resin composition and the Michael addition reaction product to be used for producing the composition. The present invention can advantageously be used in a wide variety of technical fields such as those of photo masks for etching use in the fabrication of CRT shadow masks, and lead frames for the mounting of IC chips; phosphor patterning of CRT; and further those of photosensitive resin plates, dry films, aqueous photosensitive paints, and aqueous photosensitive adhesives.
2. Description of the Related Art
Heretofore, in the manufacture of shadow masks and aperture grills for a cathode ray tube (CRT), and lead frames for the mounting of IC chips, a chrome-based photosensitive resin composition, such as a casein/chrome-based water-soluble photosensitive resin composition or a polyvinylalcohol (PVA)/chrome-based water-soluble photosensitive resin, has been used as a photoresist mask to be used in the process of etching a metal substrate. A PVA/chrome-based water-soluble photosensitive resin has also been used as a photoresist for use in phosphor patterning of CRT in a dot or stripe pattern on a transparent panel.
Specifically, for example, in the process of manufacturing a CRT shadow mask, a long metal thin plate, approximately 0.1-0.3 mm in thickness, made of 42 alloy (a nickel content of 42%), invar material (a nickel content of 36%), low carbon aluminum killed steel, or the like, is used as a substrate. Both surfaces of the substrate are defatted and washed with water, and then a photosensitive resin composition, which is generally a casein/ammonium dichromate based water-soluble photosensitive resin composition, is applied on both surfaces of the substrate, followed by drying, thereby to form a coating film. After that, a mask pattern having an objective image (pattern) to be formed is brought into close contact with the coating film, and then be exposed the double-sided film-formed substrate, covered with the mask pattern each, to light emitted from an exposure device such as an extra-high pressure mercury lamp. At that time, the masks on both side of the substrate be aligned such that the images (patterns) thereof are in register with each other. After the exposure to light, the substrate is developed using water to form patterns. Subsequently, the substrate with the patterns is dipped into a chromic anhydride solution, then washed with water. After washing, the patterned coating film is subjected to hardening by burning, thereby to form a cured photoresist pattern with increased etching-resistance. Then, an exposed or a photoresist-uncovered area of the substrate is etched with an etching solution of ferric chloride or the like (acidic etching) to form a plurality of pores through which electron beams be transmitted. After that, the photoresist pattern is stripped away, and then the substrate is cut into pieces to obtain shadow masks.
In the phosphor patterning of CRT, a phosphor (e.g., a blue phosphor) with particle sizes of ranging from several micrometers to ten-plus micrometers in diameter is dispersed and suspended in an aqueous PVA/ammonium dichromate mixed solution to obtain a slurry. Subsequently, the front surface portion (panel) of a CRT is turned in a slanting posture and said slurry is then introduced into the inner side of the panel so as to be uniformly applied, followed by drying to form a coating film. After that, the shadow mask manufactured by the above-mentioned method is attached on the panel, and then exposed to light from an extra-high pressure mercury lamp being located at the position onto which an electron gun will be placed after the completion of the CRT. Corresponding portions of the coating film to an aperture (a beam-passing opening) of the shadow mask is exposed to light. In the exposed portions of the coating film, hexavalent chromium is reduced into trivalent chromium and is coordinated with PVA, which resulted in the exposed portions be insolubilized (photo-cured). After the exposure to light, development with hot water is performed, whereby to form photo-cured phosphor patterns. In the case of a color CRT, other two additional photo-cured phosphor patterns (e.g., red and green) are respectively also formed as the same manner as described above. An extra-high pressure mercury lamp is placed at a position corresponding to an electron gun for each color.
The dichromate-containing water-soluble photosensitive resin composition to be used in the fabrication of these electronic parts is capable of forming a pattern having excellent properties of resolution, resistance to etching, and so on, although there are some disadvantages: a dark reaction is apt to occur and is strongly affected by a temperature and a humidity, whereby changes or variations in sensitivity may also occur; stability deteriorates with time and poor preservation stability is exhibited; and dichromateit is a noxious heavy metal salt, so the waste fluid processing be very complicated.
In particular, in recent years, environmental issues are pointed out more strongly than ever before, it is imperative to develop a non-chrome based water-soluble photosensitive resin composition free-from any chrome-based compound, instead of a conventional chrome-based water-soluble photosensitive resin composition containing a noxious heavy metal.
Various kinds of non-chrome based photosensitive resin compositions have been proposed until now.
The typical non-chrome based photosensitive resin compositions used as masks for etching use include (i) a casein-based photosensitive resin composition, (ii) a polyvinyl alcohol-based (PVA) photosensitive resin composition, and (iii) a photosensitive composition obtained by a ring-opening addition between a carboxyl of the side chain of a polymer or an oligomer and an epoxy-containing compound having ethylenic double bonds to introduce the ethylenic double bonds into the side chain of the polymer (oligomer).
Examples of the casein-based photosensitive resin composition described in item (i) above include a composition comprising casein and an azide compound (disclosed in JP-41-7100B), a composition comprising casein, an azide graft polymer, and naphthoquinone diazide sodium sulfonate (disclosed in JP-7-244374A and JP-8-34898A), and a compound prepared by adding organic acid calcium to a composition comprising casein and a water-soluble photosensitive material (disclosed in JP-11-119420A). However, casein tends to be perishable, therefore it should be carefully managed. Casein is coordinated with phosphor to form gel, it is not suitable for a photoresist for phosphor slurry.
Examples of the PVA-based photosensitive resin composition described in item (ii) above include a composition prepared by graft-copolymerizing PVA and vinyl monomer or carrying out addition reaction of glycidyl methacrylate into PVA, followed by adding a photosensitive component such as a tetrazonium salt, a diazo compound, or a diazo resin into the prepared PVA-based resin (disclosed in JP-44-28725B), a composition obtained by reacting PVA with a styryl pyridinium salt containing a formyl (disclosed in JP-55-23163A), and a composition comprising PVA and a condensed diazonium salt (disclosed in JP-56-42859B). However, each of these compositions is inferior to water resistance because of having hydroxyl groups in its PVA structure each. Such a composition in which a high proportion of an aromatic compound is contained, such as a diazide compound, a diazo resin, or a styryl pyridinium salt, is unsuitable for a phosphor slurry, because in ashing process for burning the photoresist off, a large amount of tarry fraction will remain at temperatures of about 400xc2x0 C. without being burned off.
Proposed examples of the composition described in item (iii) have an excellent resistance to etching, and are disclosed in JP-47-19901A, JP-48-74594A, JP-49-37701A, JP-54-12331B, JP-3-172301A, JP-9-80748A, and JP-2000-221678A.
The composition disclosed in JP-54-12331B is only of a combination of a water-soluble polymer having ethylenic double bonds in its side chain and any one selected from an anthraquinone sulfonic acid, an anthraquinone carboxylic acid and salts thereof. It is insufficient in terms of water resistance for the formation of highly minute patterns required in recent years.
Each of the compositions disclosed in JP-47-19901A, JP-48-74594A, JP-3-172301A, and JP-2000-221678A is a water-soluble alkaline composition, while the one disclosed in JP-9-80748A is an emulsion type water-soluble alkaline composition. These compositions are not completely water-soluble, and are not suitable for the development with water. In the above compositions, water-insoluble compounds are selected as the respective photopolymerizable compounds. This is because a water-insoluble photopolymerizable compound (soluble in an organic solvent) has an excellent property of water resistance after subjected to photo-induced insolubilization, compared to that of a water-soluble photopolymerizable compound. The use of the photopolymerizable compound being soluble in an organic solvent, however, may cause the problem that the compound partially separate and float on the surface of a developer in a tank after the development, thereby to give off a bad smell, which result in environment deterioration and increasing the risk of inflammability.
JP-49-37701A discloses a technology of water-solublization of a polymer or an oligomer through the reaction of a carboxyl remained in the side chain thereof with a photopolymerizable monomer to make the compound into a water-soluble quaternary ammonium salt. As the photopolymerizable monomer, N-vinyl pyrrolidone, n-butoxymethylol acrylamide, and isobutoxymethylol acrylamide are exemplified. As N-vinyl pyrrolidone is a water-soluble monofunctional monomer, polyvinyl pyrrolidone generated after the photopolymerization is also water-soluble, and the resulting pattern would be of inferior water resistance. As n-butoxymethylol acrylamide and isobutoxymethylol acrylamide are water-insoluble, even if these compounds can be dissolved in the composition, they precipitate and liberate in a developer in a tank after the development. It would entail difficulties of wasting fluid disposal associated with the use of those compounds.
Additional technologies have been disclosed in other documents. For instance, JP-56-20541B discloses a technology for making a PVA-based resist into a cured film using an iodine-containing solution. JP-57-23254B and JP-57-24905B disclose technologies for the formation of a cured film using a titanium compound after patterning with PVA and a diazo compound. However, none of these technologies can provide sufficient properties in a practical level in terms of sensitivity, resolution, etching resistance, and the like.
Thus, with the current state of the art, chrome-based water-soluble photosensitive resin compositions including casein/chrome-based and PVA/chrome-based ones are still used as a photo mask for etching use in operating conditions on production lines. Since the chrome-based compounds have excellent photosensitivities, etching resistance, and water resistance, alternative materials have been hardly found.
Examples of such a non-chrome based photosensitive resin composition to be used for phosphor patterning include a composition obtained by reacting PVA with acrolein (disclosed in JP-6-202316A), a composition comprising an acid-generating agent, and an acid cross-linkable polymer or an acid decomposable polymer (disclosed in JP-8-146598A), a composition obtained by reacting PVA with dialdehyde, dimethylol, and dialkoxy compounds and adding an acid-generating agent to the reaction product (disclosed in JP-9-319079A), a composition obtained from an ethylene-denatured PVA (disclosed in JP-10-10722A), and a composition obtained by adding an azide compound to poly(N-vinyl acetamide) (disclosed in JP-11-24241A). In addition to these compositions, non-chrome based photosensitive resin compositions for patterning are disclosed in JP-61-158861A, JP-63-64953A, JP-2-25847A, JP-8-50811A, JP-8-315637A, JP-8-227153A, JP-8-315634A, JP-10-83077A, and JP-11-84646A.
Under present circumstances, however, in the case of the photosensitive resin compositions for the phosphor patterning, PVA/chrome-based water-soluble photosensitive resin compositions are still used in operating conditions on production lines just as in the case with the above-mentioned photosensitive resin compositions for the metal etching.
The water-soluble photosensitive resin composition is inevitably subjected to a water development process for the formation of fine patterns. In particular, there is a need to form an ultra fine-pattern on the order of microns or less in the formation of CRT shadow mask pattern, the formation of mask pattern for metal-substrate etching in the process of manufacturing a lead frame for the mounting of IC chips, or the phosphor patterning of CRT. When the pattern formation is performed at such an ultra fine level, the pattern-swelling phenomenon with water becomes more remarkable, and hence, the deformation of pattern and the decrease in resolution tend to occur. Therefore, in addition to its water-solubility that allows water development, excellent water resistance is required to the resulting pattern (photo-cured pattern) after the irradiation of light. It can be said that the non-chrome based photosensitive resin compositions described above may have poorer water resistance as yet than those of the conventional PVA/chrome-based water-soluble photosensitive resin composition and the casein/chrome-based water-soluble photosensitive resin composition.
Furthermore, various kinds of new systems for display panels have been brought out in recent years. Such display panels include organic EL, inorganic EL, and field emission display panels in addition to liquid crystal display panels, which break down the field of CRT. Therefore, in forming mask patterns in the fabrication of a shadow mask and a phosphor patterning with the use of a newly photosensitive resin composition, it is desirable to successively use the currently possessed plant and equipment effectively for cost reduction, and to avoid to spend on new plant and equipment therefor.
The most preferable method is to replace the chrome-based water-soluble photosensitive resin composition currently used with another water-soluble photosensitive resin composition capable of being developed in water, and containing free from any chrome-based compound, as well as having anti-etching property to ferric-chloride solution and phosphor patterning property equally to those of the chrome-based water-soluble photosensitive resin composition currently used in the art. This is considered the best method that can be accepted in the manufacture line currently used.
The photosensitive resin composition also may be used for the fabrication of a solid flat photosensitive resin plate, a dry film, or the like.
The solid flat photosensitive resin plate is generally fabricated by applying the photosensitive resin composition on a polyester film, drying the applied resin to form a thick photosensitive layer in the form of a sheet on the polyester film, and then sticking the photosensitive layer side to a base made of steel, aluminum, polyester, or the like, followed by cutting it into a predetermined size. For providing the thusly fabricated solid flat photosensitive resin plate as a printing plate, firstly peeling off the polyester film (cover film) from the photosensitive resin plate, then a negative film is brought into close contact with the exposed photosensitive layer in a vacuum, followed by exposure with UV rays. Subsequently, the development with an organic solvent, alkaline water, water, or the like is performed, followed by drying and exposing to light. Consequently, the pattern formation is completed.
The dry film is generally fabricated by applying the photosensitive resin composition on a substrate such as a polyester film, drying the applied resin to form a photosensitive layer on the substrate, and laminating a protective film thereon. At the time of use, the protective film is peeled off and then a board (e.g., printed circuit board) is bonded on the exposed photosensitive film by a thermal compression bonding. Subsequently, the substrate (polyester film) is stripped off. Then, a negative mask is brought into contact with the exposed photosensitive layer, followed by exposure with UV rays. Subsequently, the development with an organic solvent, alkaline water, water, or the like is performed, followed by drying and exposing to light. Consequently, the pattern formation is completed.
The negative-type photosensitive resin, which is used for a photosensitive resin plate, a dry film, and so on in addition to the above-mentioned photo mask for etching use and phosphor patterning of CRT, basically may contain a binder polymer, a photopolymerizable compound, a photo initiator, and other additives. In particular, the water-soluble photosensitive resin composition may contain a water-soluble binder resin, a water-soluble photopolymerizable compound, a photo initiator, and other additives.
The negative-type photosensitive resin compositions currently used in the art are given their respective names xe2x80x9corganic solvent soluble,xe2x80x9d xe2x80x9calkaline water soluble,xe2x80x9d xe2x80x9cwater soluble,xe2x80x9d and so on. Most of them are divided into groups by what is used as a developer for each of them.
As the organic-solvent soluble photosensitive composition contains an organic-solvent soluble binder polymer and an organic-solvent soluble photopolymerizable compound, materials to be used therefor can be chosen from a wide range of options. Thus, many useful negative-type photosensitive compositions are provided. However, the use of organic solvents causes several problems such as an increase in an amount of equipment investment in order to prevent the working environment from becoming worse, such as smelling and a risk of flammability, etc. For solving these problems, it has been shifted toward the so-called water-soluble type compositions.
Among these compositions, some ones contain organic solvents, and require alkaline solutions in the process of the development. Those compositions may cause problems such as deterioration of the working environment and environmental contamination by the release of the organic solvent into the atmosphere.
Accordingly, it has been desired to provide an entirely water-soluble composition that contains none of organic solvents and is capable of being developed with water. In the field of photosensitive resin plates, for instance, those compositions are disclosed in JP-54-3790B, JP-63-64769B, and JP-61-246742A.
However, each of the compositions described in the above-mentioned patent documents has a problem of compatibility between the water-soluble binder polymer and the photopolymerizable compound, and thus the photopolymerizable compound is also selected from water soluble ones or at least water-alcohol mixture solvent soluble ones, thereby the resultant composition is of poor water resistance even after photo-insolubilization. Such a composition is hardly used in the field of printing with aqueous paint that requires water-resistance property. The plate fabricated using such composition tends to warp by swelling under the influence of high humidity in the summer, and in the winter, contrary to that, by air-drying in the winter.
The photopolymerizable compounds that are water-soluble per se and compatibilities with water-soluble binder polymers are few in number. N-vinylpyrrolidone, glycerol mono(meth)acrylate, N-methylol (meth)acrylamide, and polyethylene glycol di(meth)acrylate (the number of ethylene oxides (EO) is about 8 or more) are exemplified as those compounds, but as described above, they have poor water resistance after photo-insolubilization.
Polyethylene glycol di(meth)acrylate, which is a typical water-soluble photopolymerizable compound, exhibits water-solubility when the number of ethylene oxides (EO) thereof is about 8 or more, but poor in water resistance. When the number of EO is less than 8, improved water resistance can be attained, however, compatibility with a water-soluble binder polymer is poor, and thus, the photopolymerizable compound (EO less than 8) will sweep out from the thick photosensitive resin plate, fabricated using said compound, during storage; and in the case of formation of thin photosensitive film in the process of forming photo-mask for etching use, the photopolymerizable compound will seep out of the surface of the photosensitive film after the steps of application and drying, resulting in providing unfavorable tackiness with the surface of the photosensitive film. This adversely makes an effect on the contact exposure method in which a mask is brought into close contact with the photosensitive film at the time of exposure, and in addition, there is another problem that an unexposed portion of the photosensitive film is not dissolved in a developer (water) in developing after the exposure and the photopolymerizable compound becomes an oily film floating on the surface of the developer.
Consequently, there is the need for a negative-type photosensitive resin composition of the entirely water-soluble type: that is, the composition per se as well as a developer for such a composition is water-soluble, and is capable of forming a photosensitive film with excellent water resistance. The realization of such a negative-type photosensitive resin composition allows a wide range of applications thereof. For example, it is expected to be used in the fields of photoresists for the phosphor patterning of CRT, etching photoresists for copper wiring patterns and IC lead frames, photosensitive resin plates, dry-film photoresists, aqueous base photosensitive paints, aqueous photosensitive adhesives, and so on.
An object of the present invention is to provide a negative-type, non-chrome based photosensitive resin composition as an alternative to the conventional chrome-based water-soluble photosensitive resin composition. In particular, such a novel non-chrome based photosensitive resin composition can broadly be applicable in the fields of photo masks for etching use in the fabrication of CRT shadow masks, and lead frames for the mounting of IC chips; phosphor patterning of CRT; and further those of photosensitive resin plates, dry films, aqueous photosensitive paints, and aqueous photosensitive adhesives. In addition, the negative-type photosensitive resin composition of the present invention has water resistance as well as water-solubility, and produce effects of enduring acidic wet-etching and repetitive development in the three-color(R, G, and B) phosphor patterning process.
The present inventors eventually have found that a negative-type photosensitive resin composition comprising a product of the Michael addition reaction between a specific amino group-containing compound and a specific polyethyleneglycol (meth)acrylate could solve the above problems, and have completed the present invention.
The present inventors have also found that a negative-type photosensitive resin composition comprising a secondary product of the Michael addition reaction between the product of the Michael addition reaction and an organic silicon compound exhibited extremely excellent water resistance.
According to one aspect of the present invention, there is provided a negative-type photosensitive resin composition comprising component (A) which is a product of the Michael addition reaction between an amino group-containing compound (a-1) represented by the general formula (I): 
wherein n is an integral number of 1-4, and
a polyethyleneglycol di(meth)acrylate (a-2) represented by the general formula (II): 
xe2x80x83wherein R1 is a hydrogen or a methyl, and m is an integral number of 4-14.
According to another aspect of the present invention, there is provided a product of the Michael addition reaction to be used in the preparation of a negative-type photosensitive resin composition, wherein the product is obtained by the Michael addition reaction between an amino group-containing compound (a-1) represented by the general formula (I): 
wherein n is an integral number of 1-4, and
a polyethyleneglycol di(meth)acrylate (a-2) represented by the general formula (II): 
xe2x80x83wherein R1 is a hydrogen or a methyl, and m is an integral number of 4-14.